This invention relates to functional neuromuscular stimulation (FNS) and more particularly to improved control of FNS.
Paraplegic patients and certain other paralyzed patients who suffered from an upper motor unit spinal cord injury and undergo FNS (Functional Neuromuscular Stimulation) experience muscle fatigue within a time span that is usually shorter than is normal, but they have no sensation of this fatigue due to their paralysis. Furthermore, when FNS is used functionally, as is its implied purpose, to stand and walk, the patients need the support of a walker or canes or elbow crutches, and are unable to manually adjust FNS levels or pulse widths to compensate for that fatigue, since the time when such adjustment is necessary is exactly when the patients cannot divert attention and hands to anything else. Work on electrical stimulation of paraplegics has been done by this inventor and by others.
References include:
[1.] Kralj, A., Electrical Stimulation of Lower Extremities in Spinal Cord Injury, Proc. Nato Advance Studies Inst. On Spinal Cord Injuries, Stoke Mandeville, England, 1981;
[2.] Kralj, A. et al. Electrical Stimulation Providing Functional Use of Paraplegic Patients' Muscles, Med. Prog. Tech., Vol. 7, pp 3-9, 1980;
[3.] Liberson, W. T. et al, Functional Electrical Stimulation of the Peroneal Nerve Synchronized With the Swing Phase of the Gait of Hemiplegic Patients, Arch. Phys. Med., Vol. 92, pp 101-105, 1961;
[4.] Graupe D. et al., Patient Controlled Electrical Stimulation Via EMG Signature Discrimination for Providing Certain Paraplegics with Primitive Walking Functions, Journal Biomed. Eny., Vol., 5 pp 220-226, 1983;
[5.] Graupe, D. and Kohn, K. H. A Critical Review of EMG -Controlled Electrical Stimulation in Paraplegics CRC Crit. Rev. in Biomed. Eng., Vol. 15, pp 187-210, Mar. 1987; and,
[6.] Graupe, D. Identification of Systems, 2nd Edition, Krieges Publishing Co., Malabar, Fla., 1976.
Additionally, the present inventor has a pending U.S. patent application Ser. No. 014,389. In Reference [5], this inventor has shown that the surface (transcutaneous) response EMG as taken at the vicinity of the electrical stimulation sites in response to the stimuli applied at these sites, changes with the progression of the fatigue of the stimulated muscles during electrical stimulation.
Furthermore, it was explained in Reference [5] that the paraplegic patient has no sensation of his fatigue and of its progression, until his knee collapses from its extended (standing) position and bends, such that he falls down. When the patient's falling starts, the patient has no time nor has he the ability to use his hands nor his fingers to increase stimuli levels or sites of stimuli pulse width to overcome his fatigue. All he can do is at best to hold himself by his arms on the walker and thus achieve a somewhat controlled fall. The need for automatic monitoring of the muscle fatigue and of automatic (not manual) adjustment of stimulation to overcome this fatigue is therefore essential. A proposal for this adjustment is the subject matter of this inventor's U.S. patent application Ser. No. 014,389. In U.S. patent application Ser. No. 014,389 this adjustment is based on measuring and storing and comparing successive peaks in the response EMG and storing and comparing the time interval from the start of a given stimuli and the occurance of the peak in its corresponding response EMG signal. In many cases the peak may be higher after considerable muscle fatigue has set in, then immediately after stimulation level adjustment. In other cases no peak at all is formed prior to onset of fatigue. Hence this invention also covers situations when no peaks are considered or when the highest peak is not neccessarily occuring prior to onset of fatigue i.e., when lower peaks do not indicate progression of muscle fatigue.